I am working on laravel 5.1 project. I have updated few files for customization e.g. vendor/laravel/framework/src/Illuminate/Foundation/Auth/AuthenticatesUsers.php file. It needed to install new package so I had modified composer.json and run command 'composer update' and package was installed but all the code I had updated in AuthenticatesUsers.php file was replaced with original.
How to prevent this over-writing while updating composer?
You are not supposed to edit files in the vendor folder if you also want to use Composer to easily update your dependencies. Editing files of external packages effectively means you are forking that project and maintain it yourself. This either means you only apply your change once and then stop all further development, or you constantly have to check for updates of the original package and merge their changes with your changes.
I am pretty sure there are ways to solve the underlying problem with adding changes to existing files, but your current question suffers from the XY problem - you want to add a change to Laravel but don't know how to do properly, find that editing may solve the problem, but now need to prevent overwriting that file, and ask about preventing that overwriting - instead of asking how to add change to Laravel classes.
A nice and clean solution would be to fork the repository and add it to packagist. Then simply change the composer dependency with your version of improved (so to speak) laravel's source code.
